Still, it multiplies unchecked, as evidenced by the "Angels & Demons" ads that appeared last week. The city plans on contacting Sony's legal department after it assesses the extent of the guerrilla ads.

Mission Mission and SF Weekly started a discussion earlier this week about who really controls the billboard space in the city.

It’s a matter of public space. Whose space is it? That’s a big issue for me. You walk through the city and it’s more and more dominated by advertising. It’s getting to a point where there’s no blank space. You go to take a piss in a bar and there’s an ad. So you put a sticker on it. There’s a conversation going on out there. Most of it is talking at you; it’s not a dialogue. So whether I’m invited or not, I’m gonna participate in the conversation.